1. Field of the Invention
The present invention relates to an improvement in a lens barrel by which photographing is enabled when at least a part of a plurality of lens groups that is retracted inside a body is pushed out to a subject side in an optical axis direction, and also to an improvement of a camera, a digital camera, a portable information terminal and an image input device including the lens barrel, respectively.
2. Description of the Related Art
Conventionally, with the development of high performance of a photographic lens such as a zoom lens and miniaturization of an imaging device such as a digital camera by the request of users, the digital camera requires a photographic lens whose movable barrel is retracted into the imaging device (camera body) when not in use.
Moreover, based on the demand for reduction in thickness of the camera body, it is highly respected that the dimensions of the movable barrel, when in retracted, in a photographic optical axis direction are made minimum.
Based on the demand for reduction in thickness of the camera body, some techniques are disclosed in which at least a part of lens groups recedes from a photographic optical axis when the movable barrel is collapsed inside the camera body.
According to the techniques, since a part of lens groups recedes from a photographic optical axis when the movable barrel is retracted, the dimensions of the movable barrel in the photographic optical axis direction can be made smaller. Accordingly, the camera body can be made thicker (see, for example, Japanese Patent Publications 2003-315861 and 2003-149723).
However, the two patent Publications disclose that because a position to which the lens group has receded from the photographic optical axis is inside a maximum outer diameter of a fixed cylinder of the camera body, the dimension of the movable barrel, when retracted, in a photographic optical axis direction can be made smaller. Owing to the larger outer diameter of the fixed cylinder, some inconvenience is caused that the camera body (imaging device) looks larger, when viewed from a front (a subject in the optical axis direction).
Therefore, in order to enable photographing, at least a part of a plurality of lens groups is moved to a subject in the optical axis direction from a retracted state in which the part is collapsed to be retracted into the body. To carry this out, the following lens barrel is proposed. The lens barrel includes a plurality of lens retention frames for retaining the plurality of lens groups for each lens group, a movable barrel for maintaining the lens retention frames inside, and a retention frame drive unit for driving the lens retention frame through the movable barrel. The lens retention frame includes a receding lens retention frame by which all the lens groups are placed on a photographical optical axis when the camera is ready to take pictures, and at least one lens group is moved so that the one lens group is receded to a position that is different from one on the photographic optical axis and that is outside the maximum outer diameter for the movable barrel of the other lens groups when retracted.
It is required that this technique makes at least a part of lens groups recede from, come closer to, or move along, the photographic optical axis.
The receding lens retention frame is required to have a width of the device requested by users when the movable barrel is collapsed, and to be advanced to a position at which an image is formed when photographs are taken.
Especially with regard to a lens system having high magnification, a moving range of the receding lens retention frame is larger to the subject in the optical axis direction, compared with a lens system having low magnification. When the above technique is applied, the width of the device requested by users cannot be realized at the time the movable lens is retracted. Accordingly it is difficult to have both the width of the device requested by users and high magnification.
For the foregoing reasons, there is a need for a lens barrel that can make smaller a lens system of a plurality of lenses groups, which leads to a small width of the device, and that can make the lens system higher magnification. There is also a need a camera, a digital camera, a portable information terminal, and an image input device including the lens barrel therein, respectively.